I have found that when leading animals back, you need to go slowly and stop every bit to look back and check. Don't know if it's just me, but my leads have broken and I have to go back and pick them up and reattach to the animal and I've also just had them disappear on me. So second tip, take more than one lead when going to get an animal.

Cacti

Cacti destroys anything it touches, so if you want to harvest one, chop from the bottom up, not the top down.

Chopping Trees

If you are trying to chop down a really tall tree, put a ladder on the side of the tree, go to the top and start chopping. Then you can just jump onto the top of the tree stump and chop your way down.

Infinite Water

Make a 2 x 2 hole and put water in opposite corners.

Hot Bar

Try to keep your main objects in the same spot on your hot bar so in an emergency you don't have to look to see where they are, you can just automatically hit the button that will pull up the correct object.

Sheep Wool Colors

After making sheep of every color, I've learned some tricks so everyone can do it faster than I did.

1. Go get 2 white sheep. If you can find sheep of other colors (light gray, gray, black, brown or pink), then get them too so you don't have to make those dyes.

2. Mate your 2 white sheep as often as possible. Don't go back and get more white sheep, you don't need to waste your time.

3. Gradually start dying your sheep (using the dye chart as a guide -- http://www.minecraftwiki.net/wiki/Dyeing). Remember, if you already have sheep with colors besides white, you don't need to make that color.

4. Here's the biggest timesaving tip -- Start mating your sheep of different colors to save making some of the dyes. For instance, mate your white and red sheep to make a pink sheep. Mate your yellow and red sheep to make an orange sheep. Mate your purple and pink sheep to make the magenta sheep. Etc.

While going through a cave, place torches on the right side as you go. That way, when you're finished exploring and are ready to head back to the entrance, look for torches on your left so you know you're headed back in the right direction. Also, when you're finished exploring an area, block it off so you don't go back to the same place again. Always bring a compass with you if possible! It can be made using 4 iron ingots and 1 redstone.

You can cook things in the oven with a bucket of lava, but you unfortunately cannot make an infinite lava source in your house.

Mining Dangers

When you're mining and hear lava, ect. Don't mine, take a step, mine, take a step. Mine the full reach of your pick and then walk forward. It might just save your full set of diamond armor.

Sick of trying to find space for 500 tons of coal?! Never again with the autoloading furnace!

The trick is to make sure the hoppers point into one of the sides of the furnace (or back) so that the coal and blaze rods go into the fuel slot, not the to-be-cooked slot. If you want something to auto load into the cooking slot, you'd put a hopper on top. It provides tons of storage for fuel items and makes sure your furnace is always loaded with fuel.

Use a torch to dig out the bottom one and quickly place it after the block breaks. The rest of the sand or gravel will break on the torch. You can also use rail or redstone

Chicken breeding

Chickens can be bred in the usual manner using seeds to feed two chickens to get them to reproduce. Additionally you can collect the eggs and throw them at the ground for a chance to spawn a baby chicken (occasionally it will spawn 4 baby chickens this way). The best block to throw an egg at is a glass block as the chicken will not get 'crushed' by it if they spawn inside the block.

Enchanting

If you have an enchanting table surrounded by many bookshelves, you can reduce the maximum level of enchantment by placing torches on the bookshelves. This will remove them from the enchantment level equation.

Branch mining

Dig a big hole to the highest bedrock level (your choice of it's form). Dig a tunnel 8 blocks high and as wide and long as you like. each branch consists of 3 lots of 1x2 tunnels arranged as shown

XXOXXOXXXXOXXOXXXXOXXOXXBBB (O - dig here, B - bedrock layer)

The upper tunnel will be at the lava level and you should be able to tunnel as far as you like here (bring a bucket of water). The two lower tunnels will be underneath the lava level. Tunnel till you hit lava, block it off and turn back. You can recommence these tunnels from the top tunnel by digging down to them after the lava

Storing items

If you are running out of storage space, you can consider turning certain items into blocks. Works for iron, gold, lapis, coal, diamonds, nether quartz, emeralds and redstone (I think I got them all). Blocks are made by filling the crafting table with the item (1 in each square)

Reducing falling damage

Here's a tricky one useful for when you have to jump down a fair distance without wasting your shovels and pickaxes. There are many way's of doing this. I'm going to list a few here.

1. Place water at the top and get in. As you go down the water, pick it up again.

2. Get some dirt/cobblestone out. Aim yourself directly downwards and as you walk off the edge, hold down the right button. Right before you land, you'll place a block which will reduce the amount of damage you sustain from the fall. This one is useful if you are building something and don't want to wash away torches, disturb water flow or you just plain forgot your water bucket.

3. Get some gravel/sand and place it letting it fall to the ground. Continue till it's 1 block below you. Step on it and place the next set of gravel/sand. The idea is to build yourself a stairway down with the gravel/sand.

Placing blocks underneath a ledge

This one is difficult to do. Get some water and place it next to the ledge. Get in and let yourself sink under the ledge and place your blocks as you want. Requires a continuous pressing and releasing of space bar to remain buoyant.